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On incoming migration qemu doesn't activate the block graph nodes right away. This is to properly facilitate locking of the images. The block nodes are normally re-activated when starting the CPUs after migration, but in cases (e.g. when a paused VM was migrated) when the VM is left paused the block nodes are not re-activated by qemu. This means that blockjobs which would want to write to an existing backing chain member would fail. Generally read-only jobs would succeed with older qemu's but this was not intended. Instead with new qemu you'll always get an error if attempting to access a inactive node: error: internal error: unable to execute QEMU command 'blockdev-mirror': Inactive 'libvirt-1-storage' can't be a backing child of active '#block052' This is the case for explicit blockjobs (virsh blockcopy) but also for non shared-storage migration (virsh migrate --copy-storage-all). Since qemu now provides 'blockdev-set-active' QMP command which can on-demand re-activate the nodes we can re-activate them in similar cases as when we'd be starting vCPUs if the VM weren't left paused. The only exception is on the source in case of a failed post-copy migration as the VM already ran on destination so it won't ever run on the source even when recovered. Resolves: https://issues.redhat.com/browse/RHEL-78398 Signed-off-by: Peter Krempa <pkrempa@redhat.com> Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
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==============================
Libvirt API for virtualization
==============================
Libvirt provides a portable, long term stable C API for managing the
virtualization technologies provided by many operating systems. It
includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware
vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER
Hypervisor.
For some of these hypervisors, it provides a stateful management
daemon which runs on the virtualization host allowing access to the
API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other
languages including Python, Perl, PHP, Go, Java, OCaml, as well as
mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the
website:
https://libvirt.org
License
=======
The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.0 (or later). See the files ``COPYING.LESSER``
and ``COPYING`` for full license terms & conditions.
Installation
============
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
Contributing
============
The libvirt project welcomes contributions in many ways. For most components
the best way to contribute is to send patches to the primary development
mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
=======
The libvirt project has two primary mailing lists:
* users@lists.libvirt.org (**for user discussions**)
* devel@lists.libvirt.org (**for development only**)
Further details on contacting the project are available on the website:
https://libvirt.org/contact.html